1, The full form of RRB is Railroad Retirement Board. It’s used on Governmental ,Departments & Agencies in United States

Railroad Retirement Board (RRB) is an independent agency in the executive branch of the United States government to administer a social insurance program providing retirement benefits to the country’s railroad workers. The RRB also has administrative responsibilities under the Social Security Act for certain benefit payments and railroad workers’ Medicare coverage.

2, The full form of RRB is Regional Rural Banks. It’s used on Business ,Banking in India

Regional Rural Banks (RRB’s) were established under the provisions of an Ordinance promulgated on the 26th September 1975 and the RRB Act, 1976 with an objective to
ensure sufficient institutional credit for agriculture and other rural sectors.

3, The full form of RRB is Railway Recruitment Board. It’s used on Transport & Travel ,Rail Transport in India

Railway Recruitment Board (RRB) is primarily responsible for recruiting employes to various departments in India Railway.